Welcome to PC!
Alright, so lets talk about CP to start. So sadly in the lower levels 1-15, you are not going to really find any pokemon of a high enough CP number to really be able to do anything with other than collecting. When you get to I want to say about level 16, you will start having access to pokemon that are within the 600 CP level. If you are able to have a team of six pokemon that are all within the 600CP range you will be able to confidently take down 1000CP pokemon located in gyms.
The next thing to pay attention to is the "Line of Potential", which is the white line in the shape of a crescent over a pokemon's head. This line is telling you how close the pokemon is to meeting its max potential, which basically means the closer it is to its maximum CP number (and other stats such as HP). The further to the left this line is, the worse the pokemon, the further to the right this line is the more powerful the pokemon. This line is extremely important to pay attention to because sometimes the CP number for a lower staged pokemon might be a terribly underwhelming number compared to another, but upon evolution it might end up being humongous due to the particular species of pokemon. For example: A Drowzee with 200CP is terrible, but a Magikarp with 200CP is fantastic! The Drowzee with 200CP would have a potential line that is far to the left and would likely evolve into a weak Hypno most likely in the 600CP range. The Magikarp with 200CP likely would have a potential line that is touching the bottom of the right side, and when it evolves into a Gyarados, it will be HUGE definitely in the high 1000CP range. The line of potential is always incredibly important and will often override the actual current CP number of any pre-evolved pokemon.
Visual Example:
In general when it comes to hoarding candy and stardust. All you really need to know is, just catch everything all of the time, even if you 200 of the same pokemon and that's all you find, just transfer the pokemon that suck and hold on to the ones that have naturally huge CP numbers or have amazing potential lines. Only use Stardust on pokemon that you know are amazing or will be amazing when they evolve, or use Stardust on your favorites (which is what I often do which makes hoarding harder for me to do. lol). Catch everything, is the best advice for your current level.
Good luck and we're happy to have you in our humble community! :D